Today many children spend more of their awake time in a day care facility or other learning environment than at home. Day care rooms can be very loud. Excessive noise can adversely affect a child's hearing, language development, ability to learn, social interactions and overall well-being. There are appropriate times for high noise volume, and times when lower volume is necessary throughout a child's day. Most day care center design does not take any of this into consideration. Few states have laws or guidelines regarding such considerations, and those that do are very vague.
The intensity of sound is measured in decibels (dB). The higher the decibel, the louder the sound, or amplitude. Decibels can be manipulated by use of reflective or sound absorbent material, the shape, and form of these materials and/or building structures. For every increase of 10 decibels, sound intensity increases tenfold. For example, 20 dB is ten times as loud as 10 dB, and 30 dB is ten times louder than 20 dB. To give a basic idea of sound levels on a decibel scale, zero is the least perceptible sound. Human breathing is at about 10 dB and speech is between 50 and 70 dB. Decibels between 60 and 80 are considered to be loud, and long term exposure to 80 dB and above can cause hearing loss. Sound at about 130 dB can cause pain. To see average decibel levels for other common sounds, refer to Egan, David M., Architectural Acoustics, McGraw-Hill Book Company, 1988.
Perception to sound and sensitivity to sound and noise is unique to each individual. It is dependent on hearing ability, frequency, “time of occurrence, duration of sound, and psychological factors such as emotions and expectations” (Architectural Acoustics, 1988). Noise is unwanted sound. Any noise that is abrupt, intermittent, or fluctuates widely can be extremely annoying. Human hearing is generally less sensitive to low frequency sound. Changes in decibel levels at about 6 dB and above are clearly noticeable. It is hard for humans to disregard sound that contains speech or music.
The US Department of Labor established the Occupational Safety and Health Administration (OSHA) in 1970. OSHA's mission is “to ensure safe and healthful working conditions for working men and women by setting and enforcing standards” (http://osha.gov/about.html). OSHA enforces regulations to protect against hearing loss caused by exposure to noise in the workplace. They have established how long a person can be exposed to particular decibels in a given day. The decibels are “A” weighted, which means they are measured by an instrument that measures sound levels at the frequency of human ears, and are noted as dBA. Since then, other health organizations have adopted similar charts.
White noise, noise that is produced by combining sounds of all different frequencies together, is often used to mask other sounds because your brain cannot pick out just one sound to hear or listen too. It is often used in offices and other situations where privacy is an issue. However, white noise can sometimes be annoying to those that are sensitive to sound.
When sound strikes the surfaces of a room, part of the energy is absorbed, and part of it is reflected back into the room. Depending on the structures intended use, the amount of sound absorbed or reflected can influence the experience. The amount of sound a material absorbs is referred to as a absorption coefficient. A zero coefficient means that no sound is absorbed. Materials that absorb all of the sound have the highest rating, a coefficient of one.
You can reduce the decibels by using sound absorbing materials. These materials are porous, trapping the sound waves in tiny air-filled spaces where they bounce around until their energy dies. Examples of sound absorbing materials are drapery, clothing, fibrous ceiling tiles, and carpet.
The effectiveness of the material used for absorption is based on the physical thickness, density, porosity, fiber diameter, and orientation. The internal structure must have interconnected pores to be highly effective. An easy way to test if a material can be an effective sound absorber is to blow through it. If the material is thick and air passes with moderate pressure, it should be a good absorber.
In addition to wall, ceiling, and floor treatments, you can manipulate sound by adding baffles and clouds to the room. Both are very effective sound absorbers that work well to reduce reverberation and increase speech intelligibility. Baffles are vertical panels in which all edges and sides are exposed, placed in specific areas of the room. They work best when spaced apart. Clouds are horizontal baffles, which work in the same way. Both can be fixed in place, or movable to accommodate different functions in multi-purpose spaces.
Hard, dense surfaces such as wood, tile, and concrete, reflect more sound than they absorb. There are times when this is favorable, such as sporting events when you want the crowd to be excited, or in a concert hall, where you want the sound to reverberate in a controlled manner.
The shape of a room, baffles, diffusors, etc., along with the angle of its form, affect the way sound travels throughout a space. Sound reflects, distributes, and reverberates off different shapes and angles in different ways, and will effect the way in which the sound is distributed and received by the listener. A domed ceiling, for example, can create a whispering gallery effect. This is when a person at one corner can whisper, and the person in the opposite corner will hear clearly, while a person standing only a few feet away from the speaker cannot hear. The shape allows the sound energy to reflect along the domed ceiling surface. The whispering effect can be avoided by using a sound absorption liner. Baffles or clouds can be used to either absorb or redirect the sound, depending on the material they are composed of, and the angle in which they are hung.
The intended purpose of the room will dictate how the room is shaped, and the forms within it. For example, in an auditorium, a flat ceiling reflects sound from the stage in the front to the back with only one useful reflection.
By contrast, a sloped ceiling increases the amount of sound reflection so that the middle and rear seats receive reflections from both the ceiling planes, improving audibility throughout the auditorium.
Infants and children hear differently than adults. Children's hearing is very sensitive. Even though their inner ear is fully developed at birth, their ear canal is still very small. In turn, the sound entering into the canal has less room to develop, causing it to become much louder. Sound can be as much as 20 dB louder for infants than for adults, creating a greater chance for damage from loud noises. Auditory development continues into adolescence, progressing through three stages. The first stage happens from birth through 6 months, the second from 6 months to 5 years, and the third stage from 5 years through adolescence. During these stages it is more difficult for children than adults to hear the details of speech, to learn, and to comprehend in noisy conditions. The need for proper acoustic environments for infants and children in which to learn is emphatic.
Stage one, maturing of sound coding, happens from birth through 6 months. During this time, the middle ear is less efficient than an adult's ear in transmitting sound to the inner ear. The transmission of sound through the inner ear to the brainstem is still developing. Ability to differentiate frequencies is immature, especially high frequencies. Sound transmission through the middle ear improves greatly during the first year, then continues at a slower pace through adolescence.
Stage two, selective listening and discovering new details in sound matures between the ages of 6 months to 5 years. At six months the middle ear is much more efficient and the brain stem transmission has matured. During the age bracket of 6 months to 5 years, infants and children listen to all frequencies, while adults listen to the most useful. This makes it difficult for them to distinguish between target sounds and background noise, which in turn makes it hard for them to hear a target sound.                This finding implies that learning about sound will be more difficult for infants and preschool children in noisy environments and those in which there are several competing sources of sound . . . . The development of selective listening involves not only picking out one sound among several, but also listening to the details in complex sounds such as speech. (Lynne Werner, 2007)        
Stage Three, the maturing of perceptual flexibility takes place from 6 years through adolescents. By age 6, children are able to focus on useful parts of sound, and are not as influenced by background noise. However, the presence of noise or reverberation can make it difficult for a child to hear specific aspects of speech, even if an adult is able to hear well. For children to hear in noisy situations, more attention and processing is required, and many children cannot manage this, since the ability to process in high levels of background noise is not yet fully developed.
Affects of Noise on Children
The study of psychology and acoustics combined is called psychoacoustics, which studies the response of humans to sound. They define noise as “unwanted sound”. (Noise and Hearing Loss, OSHA, 1997-2010) What exactly makes a sound noise is different for each individual. Noise that is pleasant to some, is annoying to others.
There are times when noise is appropriate, and can stimulate wanted behavior, such as at sporting events, during exercise, and at times when enthusiastic participation is desired. However, noise can also stimulate unwanted behavior, affect physical and emotional health, and affect the way in which a child learns and develops. Noise also makes verbal communication harder, and sometimes impossible.
Physical and Emotional Affects of Noise
The most noticeable physical affect of noise is on hearing ability. It can be a temporary problem, such as at a concert, or permanent. Damage to hearing occurs in two ways. Brief exposure to an extremely loud sound like a firecracker may cause instant damage. The second is by consistent exposure to moderately loud levels of sound, (over 80 dB), that over time wear out the tiny hair cells in the inner ear. These hair cells are the nerve receptors for hearing. Signals from them are translated into nerve impulses that are sent to the brain. They do not have the ability to repair themselves, so damaging them causes permanent loss of hearing.                The number of Americans age 3 and older with some form of hearing disorder has more than doubled since 1971 (according to the National Institute on Deafness and Other Communication Disorders). US government survey data revealed that 12.5% of children ages 6 to 19 (approximately 5.2 million children) have permanent damage to their ears' hair cells caused by exposure to loud noises. (www childrenshearing.org)        
Noise can also cause an upset stomach, increase breathing rate, increases blood pressure, and make it difficult to sleep, even after the noise stops. When verbal communication competes with noise, it can strain the vocal cords.
Emotionally, noise can cause fatigue, irritability, stress, and nervousness. All of these can have an adverse affect on our ability to perform tasks and to pay attention. They may adversely affect our behavior towards ourselves or others. Excessive noise can cause a child to become withdrawn, feel overwhelmed, or over stimulated. It can cause a child to feel insecure or scared.
Noise Affects a Child's Learning and Development
Noise affects the way a child hears sounds, and speech. When their environment is loud, they have a difficult time hearing and/or distinguishing sounds and words that are new to them, or that they are unfamiliar with. This adversely affects their communication skills, and reading skills, as well as their cognitive skills.
Noise may also affect a child's ability to focus on the task at hand. Even when they appear to be playing or working on a particular task, background noise can affect how much they are really understanding in relationship to what they are doing, and cause their thoughts to wonder. It can also affect their ability to make choices, cause confusion, and misunderstanding, as well as affect a child's social interaction.
Recommended dBA Levels for Schools
Although current research shows that noise levels in schools are a detriment to children's learning and overall well being, there are no US government regulations in place regarding this issue. However, in 1998 the US Access Board joined with the ASA to develop an acoustic classroom standard. The work has been accredited by the ANSI, and is known as the “ANSI/ASA SR.60-2010 American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Parts 1 and 2” sets specific criteria for maximum background noise at 35 dBA and a reverberation time for unoccupied classrooms at 0.6-0.7 seconds. It is voluntary unless referenced by a state code. (http://www.access-board.gov/acoustic/index.htrn)
A majority of states do not have a noise standard for day care and early childhood learning centers.
The quality of a room is dependent at least in part on its acoustic properties. The acoustics of a room are a function of the geometry of the room and its floor, wall and ceiling materials. But just as important are the furnishings of the room and its occupants. Furnishings influence the acoustics of rooms and may be optimized to achieve desired acoustic characteristics in a room. The furnishing elements can take care of absorbing sound and or deflecting it. It is known to use flat absorber elements in the style of panels which are fitted in the wall and/or ceiling area to absorb sound and reduce reverberation time overall. Freestanding acoustic room dividers are also known to have a sound-directing effect. Known wall and ceiling panels are not readily integrated into a room because large wall areas can be covered by furniture immediately in front of them, because large window areas can be present and because such panels are integrated into a room's interior architecture or into the lighting design only with difficulty. Known room dividers (partition walls) require additional space and thus reduce usable room area, and they cannot be positioned in their acoustically optimum arrangement but are subject to the functional needs of the room.
Furniture is generally used to divide rooms into learning centers. The children play between them, where the noise may be trapped. But decibel readings at a child's level were as much as 5 Db. louder than readings above the furniture, at adult standing level.
Decibel Readings in Child Day Care Centers
Decibel readings were taken in 4 child day care centers. General noise in the rooms includes noise coming from other rooms, outdoor noise, HVAC systems, talking, crying, people moving about the room and centers. During group time the average readings were between 62 and 80 decibels (this includes story time and lessons). During free play time, readings ranged between 78 and 106 decibels, depending on what the children were doing. (This sound includes voices, blocks being built with and knocked down, various other toys, dress up and house play, art, and the like.) Overall day care averages were between 83 and 95 decibels. OSHA requires hearing protection be used at decibels of 85 and above in the work place, and that all employees attend hearing loss prevention work shops. If child day care centers were under the guidelines of OSHA, all of the staff and children in these facilities would be required by law to wear hearing protection!